Renal tubular absorption of D-glucose, 3-O-methyl-D-glucose, and 2-deoxy-D-glucose

Intratubular microinjection studies were performed in the rat to determine the nephron sites of reabsorption of D-glucose, 3-O-methyl-D-glucose, and 2-deoxy-D-glucose. Urinary recoveries of D-glucose averaged 4±1% from early proximal tubule sites (EPT), 27±5% from late proximal tubule sites (LPT), and 99±2% following microinjections into the distal convoluted tubule (DCT). 3-O-Methyl-D-glucose recoveries were 81±2, 89±2, and 101±5% from EPT, LPT, and DCT, respectively. 2-Deoxy-D-glucose recoveries were 77±3 from EPT, 87±3 from LPT, and 91±1% from DCT. The addition of phloridzin to the microinjection solution significantly increased the recoveries of D-glucose (84±2%) and 3-O-methyl-D-glucose (102±2%) from EPT. Recoveries of 2-deoxy-D-glucose with phloridzin averaged 92±1,93±2, and 100±2% from EPT, LPT, and DCT sites. These studies indicate that all three of the sugars studied are reabsorbed in the proximal tubule and that 2-deoxy-D-glucose has an additional site of reabsorption at a nephron site beyond the distal tubule. Phloridzin inhibits the reabsorption of these sugars, suggesting that their reabsorption is mediated by a carrier mechanism. Since prior studies from this laboratory have indicated that D-glucose and 3-O-methyl-D-glucose, but 2-deoxy-D-glucose, 2-deoxy-d-glucose, enhance sodium and water reabsorption in the proximal tubule, the present studies may indicate either that the enhancement of water reabsorption by some hexose sugars is not simply the consequence of the stimulation of a hexose-sodium transport system or that the reabsorption of some hexose sugars is not sodium dependent.